對於函數模板和類模板,模板參數並不侷限於類型,普通值也可以作爲模板參數。但非類型模板參數是有限制的,只能是常整數(包括枚舉值)或者指向外部鏈接對象的指針,浮點數、類對象和內部鏈接對象不允許作爲非類型模板參數的。
1、非類型類模板參數例子
#include<iostream>
using namespace std;
//Maxsize是一個非類型模板參數
template<typename T, int Maxsize>
class Stack{
private:
T elems[Maxsize];//包含元素的數組
int numOfElems;//當前元素個數
public:
Stack();
void push(T const& elem);
void pop();
T top() const;
bool empty() const{
return numOfElems == 0;
}
};
template<typename T, int Maxsize>
Stack<T, Maxsize>::Stack() :numOfElems(0){}
template<typename T, int Maxsize>
void Stack<T, Maxsize>::push(T const& elem){
elems[numOfElems] = elem;
++numOfElems;
}
template<typename T, int Maxsize>
void Stack<T, Maxsize>::pop(){
if (numOfElems<=0){
throw out_of_range("Stack<>::pop():empty stack");
}
--numOfElems;
}
template<typename T, int Maxsize>
T Stack<T, Maxsize>::top() const{
if (numOfElems==0){
throw out_of_range("Stack<>::pop():empty stack");
}
return elems[numOfElems-1];
}
int main(){
try{
Stack<int,20> istk;
istk.push(7);
istk.push(8);
istk.push(9);
cout << istk.top() << endl;
istk.pop();
cout << istk.top() << endl;
}catch (exception const& ex){
cerr << "Exception:" << ex.what() << endl;
return EXIT_FAILURE;
}
system("pause");
return 0;
}
2、非類型函數模板參數例子
#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
template<typename T=int,int Val>
T addValue(T const& x){
return x + Val;
}
int main(){
vector<int> vec{ 1, 2, 3, 4, 5, 6, 7, 8 };
transform(vec.begin(), vec.end(), vec.begin(), (int(*)(int const&))addValue<int, 5>);
for (auto const& c : vec)
cout << c << " ";//6 7 8 9 10 11 12 13
cout << endl;
system("pause");
return 0;
}